Credit: The Associated Press

Rafael Nadal, of Spain, celebrates after defeating Phillipp Kohlschreiber, of Germany, during the fourth round of the 2013 U.S. Open tennis tournament, Monday, Sept. 2, 2013, in New York.

NEW YORK — While Rafael Nadal was improving to 19-0 on hard courts in 2013 by returning to the U.S. Open quarterfinals, he noticed the scoreboard updates showing how Roger Federer's match on another court was going.

So Nadal knew right away that he would not play Federer next.

"When you are in the changeovers, you see what's going on," Nadal said. "But I don't (pay) attention. I just saw, and that's it."